too much nitrogen on lawn symptoms

What Happens if Grass Gets too Much Nitrogen?

In Lawn & Garden by Jamie

Nitrogen turns your grass dark green and lush, but too much nitrogen can seriously damage your lawn.

When grass gets too much nitrogen, whether through dog urine or too much synthetic fertilizer, it:

  • Burns the tips or turns grass yellow and brown
  • Lowers your lawn’s ability to withstand high or low temperatures
  • Shrivels roots, which makes it hard for them to absorb water
  • Increases the grasses’ vulnerability to disease, like leaf spot

What are the signs of too much nitrogen in the lawn?

The main signs of too much nitrogen in the lawn include:

  • Grass with brown, “burnt” tips
  • Stripes or patches of brown, green and yellow grass
  • Straw-coloured patches (generally caused by animal urine)

At the end stage, grass has turned completely brown and crunchy. When you pull on it, it comes out without any resistance. The roots look “burned”, are black, or have the consistency of mush.

If you recently fertilized with synthetic fertilizers (especially quick-release), and especially if the brown grass appears in lines, then you likely over-fertilized with too much nitrogen.

But nitrogen toxicity isn’t the only cause of yellow/brown grass. Some other causes of brown grass include:

  • Heat dormancy, where the whole lawn turns brown during the middle of summer or during a heatwave.
  • Herbicide overuse, where there’s brown patches and/or white-tipped grass blades near where you recently used herbicide.
  • Insects, disease, or buried rocks or debris, where patches of brown, straw-colored or dead grass appear.

Read our article Why is My Grass Turning Yellow and Dying? by clicking here.

How to fix too much nitrogen on the lawn?

If you’ve added too much nitrogen on your lawn, water the affected patch with 1” of water 3 to 4 times. These quick waterings will help to leach the excess nitrogen and salts from the soil without creating run-off.

If the grass has died, you’ll have to reseed. To test if your grass is dead (and not dormant), grab a handful of brown grass and pull. If it comes out easily, the grass is dead. If there’s some resistance, then the grass is dormant.

To prevent over-fertilizing:

  • Switch to fertilizing with compost. Compost has a lot less nitrogen than synthetic fertilizers, making it impossible to add too much nitrogen, and you don’t actually need as much nitrogen as lawn care companies think you do. The ideal NPK levels for a lawn are 3:1:2 or 4:1:2. And you only need to apply once a year (or twice, if you really want to give your lawn a boost). Plus compost comes with a ton of other advantages!
  • If you continue with synthetic fertilizer:
    • Measure out your lawn and calculate the square footage so you know exactly how much fertilizer you need to use.
    • Use slow-release granules rather than liquid and other quick-release fertilizers. Granule fertilizers are easier to apply evenly. Slow-release fertilizers (when used in the correct amounts) are less likely to cause nitrogen burn.
    • Use a broadcast spreader and calibrate it to release only a little at a time. Take multiple passes in different directions. The broadcast spreader tool and multiple passes will help you get a more even application (so no streaks), while the low amounts will help prevent overuse. It takes longer, but it’ll be worth it in the end.
    • And when in doubt, err on the side of using less synthetic fertilizer. The worst that can happen is that your lawn isn’t as green.

Take care when choosing what to nourish your lawn. Excess nitrogen is a lot easier to avoid in the long run than to treat.